var tmpDown; //导出的二进制对象
function downloadExl(json, type) {
	var tmpdata = json[0];
	json.unshift({});
	var keyMap = []; //获取keys
	//keyMap =Object.keys(json[0]);
	for (var k in tmpdata) {
		keyMap.push(k);
		json[0][k] = k;
	}
	var tmpdata = []; //用来保存转换好的json 
	json.map((v, i) => keyMap.map((k, j) => Object.assign({}, {
		v: v[k],
		position: (j > 25 ? getCharCol(j) : String.fromCharCode(65 + j)) + (i + 1)
	}))).reduce((prev, next) => prev.concat(next)).forEach((v, i) => tmpdata[v.position] = {
		v: v.v
	});
	var outputPos = Object.keys(tmpdata); //设置区域,比如表格从A1到D10
	var tmpWB = {
		SheetNames: ['mySheet'], //保存的表标题
		Sheets: {
			'mySheet': Object.assign({},
				tmpdata, //内容
				{
					'!ref': outputPos[0] + ':' + outputPos[outputPos.length - 1] //设置填充区域
				})
		}
	};
	tmpDown = new Blob([s2ab(XLSX.write(tmpWB, {
			bookType: (type == undefined ? 'xlsx' : type),
			bookSST: false,
			type: 'binary'
		} //这里的数据是用来定义导出的格式类型
	))], {
		type: ""
	}); //创建二进制对象写入转换好的字节流
	var href = URL.createObjectURL(tmpDown); //创建对象超链接
	document.getElementById("hf").href = href; //绑定a标签
	document.getElementById("hf").click(); //模拟点击实现下载
	setTimeout(function() { //延时释放
		URL.revokeObjectURL(tmpDown); //用URL.revokeObjectURL()来释放这个object URL
	}, 100);
}

function s2ab(s) { //字符串转字符流
	var buf = new ArrayBuffer(s.length);
	var view = new Uint8Array(buf);
	for (var i = 0; i != s.length; ++i) view[i] = s.charCodeAt(i) & 0xFF;
	return buf;
}
// 将指定的自然数转换为26进制表示。映射关系：[0-25] -> [A-Z]。
function getCharCol(n) {
	let temCol = '',
		s = '',
		m = 0
	while (n > 0) {
		m = n % 26 + 1
		s = String.fromCharCode(m + 64) + s
		n = (n - m) / 26
	}
	return s
}